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R S Cohen

Publications and source records attributed to R S Cohen.

At least 37 records · Page 2Linked to original sources
PubMed1995

The role of fs(1)K10 in the localization of the mRNA of the TGF alpha homolog gurken within the Drosophila oocyte.

A critical step in Drosophila dorsoventral patterning is the movement of gurken mRNA from the anterior cortex of the oocyte to the oocyte's anterodorsal corner at stage 8 of oogenesis. Such movement is dependent on fs(1)K10. It has been proposed that fs(1)K10 mediates gurken mRNA movement by down-regulating gurken mRNA levels, thus ensuring that gurken mRNA does not saturate its receptors located in the oocyte's anterodorsal corner. In contradiction to this model, we show here--both genetically and immunocytochemically--that GRK protein levels are lower in the anterodorsal region of fs(1)K10 mutant oocytes than in the anterodorsal region of fs(1)K10+ oocytes. From this and other data, we propose a more direct role for fs(1)K10 in the gurken mRNA localization process.

Animals↗
PubMed1995

A small predicted stem-loop structure mediates oocyte localization of Drosophila K10 mRNA.

The establishment of dorsoventral polarity in the Drosophila oocyte and future embryo is dependent on the efficient transport of K10 mRNA from nurse cells into the oocyte. To investigate the cis-requirements of K10 mRNA transport, we used a transgenic fly assay to analyze the expression patterns of a series of K10 deletion variants. Such studies identify a 44 nucleotide sequence within the K10 3' untranslated region that is required and sufficient for K10 mRNA transport and subsequent localization to the oocyte's anterior cortex. An inspection of the 44 nucleotide transport/localization sequence (TLS) reveals a strong potential for the formation of a stem-loop secondary structure. Nucleotide substitutions that interfere with the predicted base-pairing of the TLS block mRNA transport and anterior localization. Conversely, mutations that alter the base composition of the TLS while maintaining predicted base-pairing do not block mRNA transport or anterior localization. We conclude that K10 mRNA transport and anterior localization is mediated by a 44 nucleotide stem-loop structure. A similar putative stem-loop structure is found in the 3' untranslated region of the Drosophila orb mRNA, suggesting that the same factors mediate the transport and anterior localization of both K10 and orb mRNAs. Apart from orb, the K10 TLS is not found in any other localized mRNA, raising the possibility that the transport and localization of other mRNAs, e.g., bicoid, oskar and gurken, are mediated by novel sets of cis- and trans-acting factors. Moreover, we find that the K10 TLS overrides the activity of oskar cis-regulatory elements that mediate the late stage movement of the mRNA to the posterior pole. We propose the existence of a family of cis-regulatory elements that mediate mRNA transport into the oocyte, only some of which are compatible with the elements that mediate late stage movements.

Animals↗
PubMed1995

Gratuitous mRNA localization in the Drosophila oocyte.

Many of the genes that control pattern formation in Drosophila encode mRNAs that are localized to discrete regions of the oocyte during oogenesis. While such localization is generally assumed to be important for the pattern-forming activities of these genes, this has been rigorously demonstrated in only a few cases. Here we address the role of mRNA localization for the dorsoventral patterning gene K10. K10 mRNA is localized to the oocyte's anterior cortex following its transport into the cell during early stages of oogenesis. We show that mutations in cappuccino and spire, which permit K10 mRNA transport, but prevent subsequent anterior localization, do not disrupt the synthesis or localization of K10 protein. We also show that modified K10 transgenes that produce transcripts which are uniformly distributed throughout the oocyte, or which are mislocalized to the oocyte's posterior pole, produce localized and functional K10 protein. We conclude that the anterior localization of K10 mRNA is not important for K10 protein targeting or gene function. We propose that the anterior localization of K10, and probably other mRNAs, is a by-product of mRNA transport and does not necessarily reflect a requirement for localization per se.

Animals↗
PubMed1995

Old-age mortality in Israel: analysis of variation and change.

This study analyses differentials in life expectancy and cause-specific death rates among the elderly Jewish population in Israel in the early 1970s and early 1980s. We find substantial inequality in old-age mortality levels across subpopulations in geographic units and show that this inequality increased between the two periods. Much of the variation in old-age mortality is explained by differences in economic and social status, ethnicity and religiosity. The importance of religiosity is of particular interest in the context of Israeli society.

Aged↗
PubMed1994

P element transformation vectors for studying Drosophila melanogaster oogenesis and early embryogenesis.

We have constructed six new P-element-based Drosophila melanogaster transformation vectors that specifically allow for the high-level accumulation of any RNA of interest in the developing egg and pre-blastoderm embryo. Such specificity results, in part, from the inclusion in the vectors of an enhancer active exclusively in nurse cells, the principal providers of RNA to the egg and early embryo. The nurse cell enhancer was derived from the hsp26 heat-shock (HS) gene, but its activity was neither dependent on nor sensitive to HS. In addition to the nurse cell enhancer, two of the vectors contain sequences from the K10 gene that promote the early transfer of RNAs from nurse cells into the oocyte; RNAs that contain the K10 sequence are transferred into the oocyte during the early to middle stages of oogenesis (i.e., during stages 2-9), while RNAs that lack such sequences are stored in nurse cells until stage 11. All of the vectors contain a tsp and a multiple cloning site (MCS) immediately downstream from the hsp26 nurse cell enhancer. In three of the vectors, the MCS is preceded by an ATG start codon. A wild-type copy of the white gene is included in all of the vectors as a selectable marker for transformation. The specificity of the vectors was demonstrated by the analysis of the expression patterns of lacZ derivatives.

Amino Acid Sequence↗
PubMed1994

Fecal Clostridium difficile carriage among medical housestaff.

Housestaff, physician assistants, and hospitalized patients at a teaching hospital were tested for fecal carriage of Clostridium difficile. The test results showed that fecal carriage of C. difficile may not be important in the epidemiology of hospital-acquired diarrhea.

Carrier State↗
PubMed1993

Aneurysmal bone cyst of the upper maxilla.

Aneurysmal bone cyst is a nosologic entity of low frequency that appears with greater incidence in large bones. Its presence in the upper maxilla is very rare, even more so in a thirteen year old boy. The author presents the case of an aneurysmal bone cyst of the upper maxilla, together with its investigations and the surgical treatment practiced in 1987. A comment is added on the surgical technique he might adapt nowadays for approaching this type of tumors.

Adolescent↗
PubMed1992

Trisomy 22 with congenital diaphragmatic hernia and absence of corpus callosum in a liveborn premature infant.

We report on a liveborn premature male with trisomy 22 who had multiple congenital anomalies, including congenital diaphragmatic hernia and absence of corpus callosum. He died of pulmonary hypoplasia associated with diaphragmatic hernia within 12 hours of age. Chromosome analysis by multiple banding techniques based on lymphocyte culture confirmed that he had trisomy 22. This may be the first report of congenital diaphragmatic hernia and isolated absence of corpus callosum associated with trisomy 22.

Abnormalities, Multiple↗
PubMed1992

The effects of dark-rearing on the electrophysiology of the rat visual cortex.

Our previous two studies have shown that dark-rearing affects the morphology and chemistry of adult rat primary visual cortex (area 17). In this study we demonstrate correlated physiological alterations with single unit recordings in the same preparation. Rats were raised from birth in either 14 h light/10 h dark (Lt/Dk) or in total darkness (Dk). At the age of 3 months, single units were recorded in area 17 of both groups. The cortical cells of Dk animals showed significantly more spontaneous activity during ambient lighting. The mean rate of randomly appearing spontaneous activity was greatly increased in Dk animals. Moreover, many cells in Dk animals also exhibited a particular type of spontaneous activity which occurred as 'bursts' of spikes, i.e. quantified groupings of fast firing spikes, separated by randomly appearing spontaneous activity. The mean number of bursts per min seen in Dk animals was also significantly more than any such activity seen in Lt/Dk animals. Visual stimuli consisted of white or dark bars moving with different orientations and directions at slow and fast speeds, and full field flashes. In response to moving stimuli, notably fewer cells were orientation- or direction tuned in dark-reared animals, and when they did respond to moving bar stimuli, the responses were of relatively longer duration. The pathologically high spontaneous activity rate, as well as lack of tuning and relatively prolonged duration of responses to moving stimuli indicate that intracortical inhibitory mechanisms are seriously compromised in both the unstimulated and stimulated states and is in agreement with our previous findings (Bakkum, B.W., Port, J.D., Cohen, R.S. and Benevento, L.A., Soc. Neursci. Abst., 15 (1989) 797) of a decreased number of synapses and GABA-containing cells in the visual cortex of the same preparation. Other evidence suggests that there may be a decrease in stimulus-bound excitatory drive. Significantly fewer cells in Dk animals were excited by all visual stimuli, and responses elicited by flashes had relatively longer 'on' latencies, relatively shorter durations, and were generally weaker. This may correlate with our finding of a significantly smaller number of perforated postsynaptic densities in the cortex of the same preparation (Bakkum, B.W., Benevento, L.A. and Cohen, R.S., J. Neurosci. Res., 23 (1991) 65-80).

Action Potentials↗
PubMed1992

Identification and characterization of Drosophila female germ line transcriptional control elements.

The highly organized structure of the Drosophila ovary makes it an ideal system for studying mechanisms of differential gene expression. Here we report the identification of a 171 bp sequence from the 5' end of the hsp26 gene that functions as a female germ-line-specific transcriptional regulator when linked in two copies to a basal promoter. The regulator is active only in nondividing cells of the germ line, i.e., only in nurse cells and oocytes. It is not active in any examined tissue or cell type outside of the female germ line. Copper nuclease footprinting studies show that the germ line regulator contains two binding sites for each of two different ovarian nuclear factors. Point mutations in the DNA target sites of either nuclear factor abolish in vitro binding and in vivo transcriptional activity, indicating that each factor is a positive activator of nurse cell/oocyte transcription. The two factors may represent different classes of activator proteins, since an increase in the copy number of one factor's DNA target site cannot compensate for a decrease in the copy number of the other factor's target site.

Animals↗
PubMed1992

Evidence for a highly selective RNA transport system and its role in establishing the dorsoventral axis of the Drosophila egg.

The specification of cell fates along the dorsoventral axis of the Drosophila embryo is dependent on the asymmetric distribution of proteins within the egg and within the egg's outer membranes. Such asymmetries arise during oogenesis and are dependent on multiple cell-cell interactions between the developing oocyte and its neighboring somatic follicle cells. The earliest known such interaction involves the generation of a signal in the oocyte and its reception in the follicle cells lying on the dorsal surface of the oocyte at approximately stage 10 of oogenesis. Several independent lines of investigation indicate that the fs(1)K10 (K10) gene negatively regulates the synthesis of the signal in the oocyte nucleus. Here we present data that indicate that the accumulation of K10 protein in the oocyte nucleus is a multistep process involving: (1) the synthesis of K10 RNA in nurse cells, (2) the rapid transport of K10 RNA from nurse cells into the oocyte, (3) the localization of K10 RNA to the anterior margin of the oocyte, and (4) K10 protein synthesis and localization. K10 RNA is transported into the oocyte continuously beginning at approximately stage 2. This indicates a high degree of selectivity in transport, since most RNAs synthesized in stage 2 and older nurse cells are stored there until stage 11, when nurse cells donate their entire cytoplasm to the oocyte. The sequences responsible for the early (pre-stage 11) and selective transport of K10 RNA into the oocyte map to the 3' transcribed non-translated region of the gene. None of the other identified genes involved in dorsoventral axis formation are required for K10 RNA transport.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Effects of light/dark- and dark-rearing on synaptic morphology in the superior colliculus and visual cortex of the postnatal and adult rat.

Several synaptic parameters, previously shown to undergo alterations with changes in the internal and external environment, were examined in the visual system of light/dark- and dark-reared postnatal and adult rats. Animals were raised in either 14 hr light/10 hr dark (Lt/Dk) or in total darkness (Dk). The specific synaptic parameters in the superficial layers of the superior colliculus (SC), visual cortex (laminae II/III and IV) (VC), and, as control, the auditory cortex (laminae II/III and IV) (AC), examined during the postnatal period (i.e., postnatal days 7, 14, 21, and 28) and in the adult (i.e., day 56) included: 1) mean number of synapses, 2) mean synaptic length, 3) percentages of perforated postsynaptic densities, 4) percentages of asymmetric and symmetric synapses, 5) percentages of dendritic, spinous, and somatic synapses, and 6) percentages of synapses with positive, negative, or no curvature. Developmental patterns in rats reared in normal lighting conditions were noted. Specifically, in the SC and VC of Lt/Dk animals, the number of synapses increased up to postnatal day (PND) 21 and then decreased; no significant changes in the mean number of synapses between PND = 28 and 56 were detected in any of the areas examined. Changes in synaptic length in the SC and VC were not observed during postnatal development of in the adult in any of the aforementioned brain areas. Low percentages of postsynaptic densities (PSDs) were found at all time points and in all brain areas during the postnatal period. Increases in perforated PSDs were seen at PND=56 compared to PND=28 in the VC. In the VC and AC, there was a decrease in symmetric synapses with age. Asymmetric synapses were prevalent in all brain areas at PND=28 and 56. Dendritic synapses predominated in the SC, while spinous synapses were the preponderant type in the VC and AC during postnatal development and in the adult. A decrease in the percentage of spinous synapses in the SC was observed at PND = 56 vs. PND=28. A decrease in the percentage of negatively curved synapses with age and a trend toward a concomitant increase in the percentage of positively curved synapses were seen in all brain areas during development and in the adult. Quantitative analyses of the SC and VC tissues examined from all postnatal animals demonstrated no significant differences between Lt/Dk and Dk animals in all the synaptic parameters measured.(ABSTRACT TRUNCATED AT 400 WORDS)

Age Factors↗
PubMed1991

Effect of vascular puncture on blood gases in the newborn.

Continuous monitoring methods have shown changes of oxygenation in neonates during various procedures. However, actual changes in blood gases during vascular punctures have not been reported. We studied the effect of vascular puncture on arterial blood gases during routine venipuncture in 17 neonates who had indwelling arterial catheters. Arterial blood gases were analyzed before, during, and following recovery from venipuncture. Ventilator settings were not changed during the study, though oxygen concentration (FiO2) was adjusted as indicated by continuous PO2 or saturation monitors. During venipuncture, there was a significant fall in PaCO2 from 38 +/- 5 to 32 +/- 7 mmHg (P less than 0.0001) and in PaO2 from 75 +/- 21 to 58 +/- 23 mmHg (P less than 0.0001). Following venipuncture, both values returned to baseline. The results of this study imply that blood gases obtained by intermittent arterial sticks may provide data that do not accurately reflect the neonates' respiratory status.

Blood Gas Monitoring, Transcutaneous↗
PubMed1991

Localization of ATPase activity in dendritic spines of the cerebral cortex.

An ATPase activity has been demonstrated in dendritic spines of the adult rat cerebral cortex using cerium to capture inorganic phosphate that is liberated during the enzymatic hydrolysis of ATP. Small pieces of cerebral cortex were fixed and incubated in a standard incubation medium containing both Ca2+ and Mg2+ at pH 7.2; other modifications of the incubation medium are described below. Electron microscopic examination of the cerium phosphate reaction product showed an electron dense precipitate localized in the cytoplasm of the spine behind the postsynaptic density. Whereas the postsynaptic density, itself, is not reactive, dense reaction product is seen immediately underneath the postsynaptic density and extending into the subsynaptic web. Reaction product is also associated with membranous cisternae within the dendritic spine. The reaction occurred in the presence of Ca2+ and Mg2+ and either of these two ions alone. However, virtually no reaction product is seen when the tissue was incubated in a medium devoid of Ca2+ and Mg2+, or in a medium containing Mg2+ and EGTA, suggesting that trace Ca2+ is necessary, but not sufficient for the reaction. Addition of p-chloromercurobenzoate, which selectively blocks SH groups, inhibited the reaction in the presence of Ca2+ and Mg2+, or both of these ions. The effect of pH on the reaction was determined using a lead precipitation method. The reaction occurred at pH 9.2 in the presence of Ca2+ alone. In the presence of Mg2+ alone, the reaction product appeared somewhat reduced at this pH. The presence of an ATPase activity, which is dependent upon Ca2+ in dendritic spines where actin and actin-binding proteins have also been localized, suggests that this activity may be involved in the dynamics of cytoskeletal function leading to shape changes in dendritic spines and synapses, as seen with various physiological and behavioral paradigms.

Adenosine Triphosphatases↗